1. Field of the Invention
The present invention relates to electrical connectors, and more particularly to a land grid array (LGA) socket for electrically connecting a central processing unit (CPU) to a printed circuit board (PCB).
2. Description of the Prior Art
An integrated circuit (IC) package having leads arranged in a land grid array (LGA) is known as an LGA package. LGA packages have relatively low height, which saves valuable space in electronic assemblies.
Connectors for removably mounting an LGA package on a PCB are known as LGA sockets. An LGA socket combined with ball grid array (BGA) technology typically comprises a thin and substantially flat insulative housing which is positioned between the LGA package and the PCB. The housing defines an array of passageways receiving electrical contacts therein. The contacts correspond with the array of leads of the LGA package. Each contact has a pair of opposite free ends that project beyond opposite external surfaces of the housing. Prior to mounting of the LGA package, the free ends are spaced apart a predetermined distance. The free ends are respectively engaged with corresponding contact pads on a bottom surface of the LGA package, and soldered to contact pads on a mounting surface of the PCB.
Various LGA sockets combined with BGA technology are disclosed in, for example, U.S. Pat. Nos. 6,132,220, 6,179,624 and 6,203,331. One problem encountered with such conventional sockets is that during heating of solder to attach the socket to the PCB, a bottom surface of the socket may not be parallel to the PCB due to asynchronous melting of the solder balls. Molten solder may upwardly wick into the passageways of the socket and thereby adversely affect electrical performance of the contacts.
Improved CPU sockets devised to overcome the above problems are disclosed in U.S. Pat. Nos. 6,152,756 and 6,220,884. Referring to FIG. 1, a typical such CPU socket 6 comprises a plurality of spaced standoffs 61 depending beyond a bottom surface of the socket 6 toward a mounting surface of a PCB 7. When solder balls 62 are heated and melted, the standoffs 61 abut against the top surface of the PCB 7. The socket 6 is thus distanced a predetermined height above the PCB 7, with a bottom surface of the socket 6 being parallel to the top surface of the PCB 7. Accordingly, the melted solder balls 62 are prevented from wicking into the passageways 63 of the socket 6.
However, the standoffs 61 integrally extend from the bottom surface of the socket 6, and heights of the standoffs 61 are slightly less than heights of the solder balls 62. When downward force is applied to a top surface of the socket 6, the force is immediately transmitted to the solder balls 62. Thus the solder balls 62 are liable to collapse under such force before the standoffs 61 can abut against the top surface of the PCB 7 and counteract the force.
Therefore, an improved CPU socket which overcomes the above-mentioned problems is desired.
Accordingly, an object of the present invention is to provide an electrical socket having flexible standoffs which prevent damage to solder joints between the socket and a PCB.
Another object of the present invention is to provide an electrical system including an electrical package, an electrical socket and a PCB, wherein the socket can be safely and reliably mounted on the PCB when the electrical package is mounted on the socket.
A further object of the present invention is to provide supporting members for an electrical socket so that the electrical socket can be accurately aligned to be parallel with a PCB.
To achieve the above objects, an LGA socket in accordance with a preferred embodiment of the present invention comprises a low-profile insulative housing and a plurality of electrical terminals. The housing has a top surface and an opposite bottom surface. A plurality of passage ways is defined in the housing between the top and bottom surfaces. Each passageway has one electrical terminal received therein. Each terminal has a contact portion protruding beyond the top surface of the housing, and a solder portion extending toward the bottom surface of the housing. The solder portion is connected with a solder ball, and the solder ball can be soldered to a PCB. A pair of receiving slots is defined in opposite sides of the housing. Each slot has a flexible supporting member disposed therein.
Each supporting member comprises a base portion connecting with the housing, a pair of cantilever arms extending in opposite directions from the base portion, and a deflectable supporting block formed at a free end of each of the arms. Each supporting block has a first supporting portion protruding beyond the top surface of the housing, and a second supporting portion extending toward the bottom surface of the housing. The supporting block can deflect in the slot relative to the base portion of the housing, and thereby support the socket on the PCB.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: